We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
MANAGERS AND PROJECTIONISTS 827
condenser showing in a motion picture, whereas it shows plainly in a stereo picture. See page 443, first volume.
To this we might add that the reason some makes of reflector type lamp use only one side of the mirror for slide projection is because the long focal length stereo.projection lens has such great depth of focus that if the center of the mirror were used it would include in the screen image an out-of-focus image of the carbons and their holders.
SIZE OF MIRROR.— Referring to Fig. 309A it will be observed that the diameter of the mirror or reflector does not necessarily indicate the angle, or amount of light "picked up" and reflected back. A small diameter mirror may actually pick up and utilize as much or more light than the larger one, provided the light source be close enough to its surface, and the curvature of the mirror be such as will focus all the reflected light at its correct point in the spot at the projector aperture. However, there are, of course, limitations beyond which it is impossible to go, because of the high temperature of an electric arc light source.
DANGER FROM OPENING NON-EXISTENT.— In the reflector are lamp using spherical mirror, the opening in the front of the lamphouse where the condenser ordinarily is, is entirely open and free. Some officials have feared that this would add to the fire hazard. In our opinion they are in error, insofar as has to do with the escape of sparks from the carbon, because even the most light incandescent particles of carbon could hardly, by any conceivable chance, escape through the opening and reach the film. Moreover any particle of incandescent matter light enough to float in air, would not have sufficient heat to set fire to film, especially since it would not come into direct contact with anything but the photographic emulsion, which is not especially inflammable ; also it is an important fact that, in the very nature of things, there is always a strong current of air entering through the opening at the front of the lamphouse, which passes up through the vent flue.
HEAT OF THE SPOT.— That there is added heat at the spot by reason of the absence of a condenser, or by reason of the reduction of the thickness of glass brought about by the substitution of one thin condenser lens for two thick ones, is true. It is a fact that the reflector arc lamp operating at twenty-five amperes produces fully as hot a spot as does the high amperage ordinary arc. It is even claimed by some that it